Definition of multiway
What is meant by multiway is a multi-player hand. The majority of these pots's will be the pots limp, i.e. the pots's in which no one has raised preflop's. The majority of the pots's in Hold'em are played one-on-one after the flop. There are also the pots's that are called 3-way, when 3 players see the flop and from 4 or more players, we can really talk about pot multiway.
How to play the pots multiway?
There is no magic recipe to play the pots multiway, but let's just say that the best advice we could give you is to play the pots in a more conservative way. You can always bluff one or two players after the flop, but when you're say 5 to flop, your bluffs will be much less successful and you're probably better off not calling them in the pots multiway (we'll also say family). The average hand that's going to win the pot at the slaughter will also be stronger when you're in a pot multiway. If you can win a jackpot with a top pair in a one-on-one, in the pots multiway's it will be rarer.